Answered by Sayyidi al-Ḥabīb `Umar bin Hafīẓ (may Allāh preserve him and benefit us by him).
What should we read in the Rawḍah or in front of the Ka`bah?
There are booklets compiled on supplications to be read at these times, such as al-Ḥiyāḍ al-Muṭṭahharah li Zā’ir al-Madinah al-Munawwarah and Zād al-Nāsik (both by Habib `Umar). [Zad al-Nasik may be downloaded from Habib `Umar’s website http://www.alhabibomar.com/Book.aspx?SectionID=6&RefID=213].
The recently published book, Ḍajīj al-Muliḥḥīn, also contains many supplications.
However, if Allāh inspires you to make a certain supplication then this should be given priority.